1. Field of the Invention
The present invention relates to slide fasteners, or zippers, for sport shoes, and particularly for cross-country skiing.
2. Description of Background and Relevant Information
The use of slide fasteners on shoes is common because of their practicality. Such fasteners have a general imperviousness to exterior influences because of the slider which extends continuously on the upper of the shoe. The slider is easy to maneuver for opening and closing, and the mounting of the slide fastener avoids the covering of areas of the shoe by two layers of material in areas of the shoe where the foot of the wearer bends, as is the case of fasteners of the "hook and loop" type or buttons. Examples are the shoe model "CS 420" shown in the catalogue "TRAK 86-87", as well as the shoe disclosed in the patent for Italian Industrial Design No. 193 252 wherein the fastener is of the "hook and loop" type. In these shoes, the area of the upper which closes the shoe on the foot covers the opposite area on which it is fastened over a wide area. In such constructions, not only does the necessity of covering the closure area lead to additional layers of material and thus a higher cost, but the covering of the closure area affects the flexibility of the upper because of the superposition of material which substantially doubles the thickness of the wall of the upper in the closure area.
For the above reasons, slide fasteners are often preferred over other types of fasteners. For example, the shoes described in the British patent documents Nos. 531,776 and 380,909, the French application for certificate of usage No. 2,549,701, and U.S. Pat. Nos. 2,444,640 and 2,970,390 use slide fasteners. The shoes illustrated in these documents have at least one slide fastener, arranged on the upper anterior part of the upper of the shoes. These slide fasteners are essentially oriented along the longitudinal axis of the shoe or parallel thereto. In the particular construction of U.S. Pat. No. 2,444,640, the fastener wraps around the upper anterior part of the upper and retains it on the lower part of the upper.
These shoes are relatively convenient to put on and to remove. However, they have significant disadvantages for use in a sport, particularly when the foot must bend in a repeated intensive fashion by flexing, such as is in cross-country skiing or running. In effect, the slide fasteners are relatively inflexible in the longitudinal direction of their mounting, and this mounting on the upper in the longitudinal direction appreciably hinders bending or flexing. The variation in curvature and the folding of the material of the upper causes significant variation of pressure, particularly on the anterior part of the foot between the top of the instep and the metatarso-phalangeal articulation area. This can cause discomfort and the advent of localized pain.
The present invention eliminates the disadvantages of shoe fasteners having a covering of the upper areas of the upper, and more particularly, the disadvantages relating to slide fasteners by eliminating the large deformations of the slide fastener when flexing the upper during bending of the foot.